The present invention relates to switching of optical signals, and, in particular, to spatial routing of optical signals transmitted in optical communication networks and optical signal processing.
Optical fibers are used as the physical media for transmitting optical signals in a variety of commercial and military applications. As the data rates of information continue to grow, it becomes increasingly difficult for conventional electronic switching systems to handle higher bandwidths. In addition, the required conversion between optical and electrical signals restricts the data format and increases costs. All-optical routing/switching technologies, characterized by high xe2x80x9cdata transparency,xe2x80x9d can switch or transfer optical signals from one transmission channel to another while the signals remain in optical form. Several multiplexing schemes have been developed in fiber optic interconnection networks, including time-division multiplexing (TDM), wavelength-division multiplexing (WDM) and space-division multiplexing (SDM). Space-division switching is considered to be one of the most important fiber optic routing schemes. Major applications of space-division photonic switches are in fiber optic communication networks, optical gyroscopes, optical signal processing, and micro/millimeter wave signal distribution, e.g., for phased-array radar systems.
A wide variety of electromagnetic field-controlled optical switches are commercially available. They are based on mechanical, electro-optic, thermo-optic, acousto-optic, magneto-optic, and semiconductor technologies. Each switching technology has its own advantages, but also has drawbacks as well. For example, mechanical switches are the most widely used routing components and provide very low insertion loss and crosstalk characteristics, but their switching time is limited to the millisecond range. They also have a limited lifetime because motor-driven parts are used. LiNBO3 optic switches, on the other hand, offer nanosecond switching times. However, LiNbO3 4xc3x974 switches suffer from the disadvantages of relative large insertion loss (5 dB), high crosstalk (25 dB) and polarization dependency.
Accordingly, efforts continue to develop field-controlled optical switches with lower channel crosstalk, reduced polarization dependent loss, and at least moderate reconfiguration speed. It is recognized that these efforts, when successful, can provide an important component to fiber communication systems.
Optical switches are often assembled from a number of components typically requiring the components to be precisely aligned, coupled, or otherwise positioned. Such assembly has relatively high costs, including high labor costs involved in precision assembly, high material and component costs, high maintenance and repair costs and the like. Accordingly, it would be useful to provide optical switching devices which permit the number or variety of components in such switches to be reduced, in some cases eliminating certain types of components all together.
Switch arrays are provided with controllable polarization modifiers and polarization-dependent diverters, such as one or more polarization beam splitters, for configuring switch arrays which can reduce or eliminate the need for optical fibers in the switch arrays. In one embodiment, input positions configured in a first preferably planar (e.g., horizontal) configuration are routed to one or more of a corresponding plurality of output positions which are configured in a different arrangement such as in an orthogonal (e.g., vertical) planar arrangement. Preferably some or all of the polarization-related optical components, including components such as birefringent devices, liquid crystal polarization rotator arrays and/or polarization beam splitters are integrated so that one such device can be used in connection with a plurality of input and/or output beams.